I thought this was a complete waste of time (I own the fitbit wireless pedometer/altimeter tracker - considered a companion product to this device) until I read " four sets of ITO electrodes shoot a small — 180 micro amps, small — imperceptible current up one leg and down the other to measure body impedance, and thus, your body's fat versus lean mass composition" now it seems pretty damn cool, you can view all your progress as stats or graphs via your phone (apps for android and iphone) or via the website.

and the companion fitbit ultra is excellent - I wear it to track sleep (via a comfy arm band) and I wear it to track my daily milage on foot which includes height climbed via its altimeter. It can also tell dummy exercise from real (if you stand on the spot and try to simulate walking or jogging) via a set of 3d sensors more kitted out than a Wii remote. it needs charging once a week,just by sitting on its computer attached dock and it will send stats every 15 min when within 15 min of the dock so you will automagically get emails congratulating you on things like the first time you clocked 20000 steps in a day or climbed 10 staircases. also very easy to choose to compete with friends and compare metrics.

I think body impedance measurements can be affected by how hydrated you are, or if your feet are wet etc. So may not be all that accurate. Though it should be fairly consistent if you used them at the same time of day, and would give you an idea of the overall trend.

I do want one of those wifi scales, that can log to a website or app etc. How does this one compare to other makes, eg Withings or Tanita? They are all rather expensive.